Polyamide-rubber blended composition

ABSTRACT

The present invention describes a polyamide-rubber blended composition having improved resistance to ozone, stress whitening and gasoline prepared by mixing together with heating the following components: 
     (a) from 70 to 20 volume percent of a rubber composition consisting of: 
     (i) 30 to 70 volume percent of an acrylonitrile-butadiene copolymer containing at least 0.7 weight percent of a carboxyl group in the polymer, and 
     (ii) 70 to 30 volume percent of an epichlorohydrin rubber; 
     (b) 30 to 80 volume percent of a polyamide resin; and 
     (c) at least 0.1 parts by weight of a polyepoxy compound in terms of the weight of the epoxy group per 100 parts by weight of the rubber composition of component (a), 
     components (a) and (b) blended together after which component (c) is added and the resulting mixture kneaded with heat to form the polyamide-rubber blended composition.

FIELD OF THE INVENTION

The present invention relates to a polyamide-rubber blended compositionhaving improved characteristics with respect to strength, flexibilityand resistance to ozone, stress whitening and gasoline.

BACKGROUND OF THE INVENTION

Polyamide resins are recently attracting the attention of researchers asmaterials for producing more durable and lighter automotive hoses suchas gasoline supply hoses. However, since polyamide resin hoses are notas flexible as rubber hoses, efforts are being made to provide highflexibility to the polyamide resins by one of the following threemethods: the addition of a plasticizer to the polyamide resin; blendingrubber with the polyamide resin; and block and/or graft polymerizing adissimilar monomer onto the polyamide resin. However, the use of aplasticizer is not practically feasible because the plasticizervaporizes with heat or is extracted with gasoline and other oils orsolvents, causing a significant drop in the flexibility of the polyamideresin. The block and/or graft copolymer prepared by the third method hasa low melting point and is not suitable for high-temperature use whichis the principal intended application of the polyamide resin.

In order to permit use in applications where contact with gasoline andother oils or solvents is expected, the rubber for use as component tobe blended with the polyamide resin in the second method is selectedfrom acrylonitrile-butadiene copolymer rubber (for convenience this willsimply be referred to as nitrile rubber) and epichlorohydrin rubber(hereunder simply referred to as hydrin rubber). Japanese patentPublication No. 14096/1980 and U.S. Pat. No. 4,173,556 show a method inwhich a blend of the nitrile rubber and polyamide resin is mixed with across-linking agent with heating so that the nitrile rubber is dispersedin the polyamide resin while the rubber is being cross-linked.Similarly, Japanese Patent Application (OPI) No. 5753/1982 and U.S. Pat.No. 4,297,453 show a method in which a blend of the hydrin rubber andpolyamide resin is mixed with a cross-linking agent with heating so thatthe hydrin rubber is dispersed in the polyamide resin while the rubberis being cross-linked. However, the nitrile rubber impairs significantlyan inherent high resistance to thermal aging of the polyamide resin,further the hydrin rubber reduces the good strength properites of thepolyamide resin.

The present inventors previously proposed in Japanese Patent ApplicationNo. 41576/1983 (corresponding to U.S. application Ser. No. 589,223 filedon Mar. 13, 1984) a method for preventing the drop in the resistance tothermal aging and strength properties of a polyamide resin by blending apolyamide resin with two other polymers, i.e., nitrile rubber and hydrinrubber. However, the resulting blend is inferior to the polyamide resinper se in respect of resistance to ozone, upon the cyclic application oflarge strains, and resistance to stress whitening under appreciablelocal strains. Therefore, this three-polymer blend is not satisfactoryfor use for parts which are subject to significant vibrations or extremestrains.

Therefore, the present inventors continued their studies on producing apolyamide-rubber blended composition which has improved resistance toozone and stress whitening, as well as high strength and flexibility,and significant resistance to thermal aging as well as gasoline. As aresult, it has been found that the desired composition can be producedby the present invention.

SUMMARY OF THE INVENTION

The primary purpose of the present invention is to provide apolyamide-rubber blended composition having improved resistance to ozoneand stress whitening, as well as high strength and flexibility, andsubstantial resistance to thermal aging and gasoline.

The polyamide-rubber blended composition of the present inventioncomprises:

(a) 70-20 vol% of a rubber composition consisting of (i) 30-70 vol% ofan acrylonitrile-butadiene copolymer rubber containing at least 0.7 wt%of a carboxyl group in the polymer and (ii) 70-30 vol% of anepichlorohydrin rubber;

(b) 30-80 vol% of a polyamide resin;

(c) at least 0.1 parts by weight of a polyepoxy compound in terms of theweight of the epoxy group per 100 parts by weight of the rubbercomposition specified in (a).

provided that components (a) and (b) are mixed first, followed by theaddition of component (c), and the resulting mixture then is kneadedunder heating.

DETAILED DESCRIPTION OF THE INVENTION

The carboxyl-containing nitrile rubber (hereunder referred to ascarboxyl nitrile rubber) in component (a) of the composition of thepresent invention is a copolymer of acrylonitrile, butadiene and acarboxyl containing monomer such as methacrylic acid, acrylic acid,maleic acid, or fumaric acid, or a copolymer wherein acrylonitrile andbutadiene as the major components are polymerized with acrylate ester orisoprene and the carboxyl containing monomer. In either case, thecarboxyl nitrile rubber contains at least 0.7 wt%, preferably not lessthan 2 wt%, of a carboxyl group in the polymer. If the carboxyl groupcontent in the polymer is less than 0.7 wt%, the ozone resistance of thefinal composition is appreciably reduced. The carboxyl nitrile rubberpreferably has a glass transition point of 10° C. or less and a boundacrylonitrile content of 10-55 wt%, and those having the boundacrylonitrile content of 30-50 wt% are particularly preferred in view ofcompatibility with an epichlorohydrin rubber.

The epichlorohydrin rubber in component (a) of the composition of thepresent invention may be a homopolymer of epichlorohydrin, a copolymerof epichlorohydrin and ethylene oxide or propylene oxide, or aterpolymer of epichlorohydrin, ethylene oxide or propylene oxide andallylglycidyl ether.

If the rubber composition of component (a) consisting of the carboxylnitrile rubber and epichlorohydrin rubber is less than 20 vol% of thetotal volume of the rubber composition and the polyamide resin, theeffect of the rubber composition's improvement of the flexibility of thepolyamide resin is not exhibited to the fullest extent. If theproportion of the rubber composition exceeds 70 vol%, thethermoplasticity of the polyamide resin is impaired and the resultingblend has poor processability.

The polyamide resin as component (b) of the composition of the presentinvention is a crystalline thermoplastic resin having an amido bond inthe polymer. Examples of this polyamide resin are hopolymers such aspolycaprolactam (nylon 6) and polylauryllactam (nylon 12), andcopolymers such as the condensation polymer of 11-aminoundecanoic acid(nylon 11), polyhexamethylene azelamide (nylon 6,9) andpolyhexamethylene sebacamide (nylon 6,10) as well as polyamide resinsprepared by block and/or graft copolymerization of these comonomers withother monomers. Preferred polyamide resins are those onto which adissimilar monomer is block and/or graft polymerized in such an amountthat it does not greatly reduce the melting point of the polyamideresin.

The proportions of the carboxyl nitrile rubber and hydrin rubber to beblended to form the rubber composition (a) are such that the carboxylnitrile rubber is 30-70 vol%, preferably 40-60 vol%, of the total volumeof the two rubbers, and the hydrin rubber is 70-30 vol%, preferably60-40 vol%, on the same basis. If the carboxyl nitrile rubber is morethan 70 vol% or less than 30 vol%, the ozone resistance of the finalcomposition is appreciably reduced. If the amount of the carboxylnitrile rubber is less than 30 vol%, the resistance to stress whiteningof the composition is also decreased by a significant degree.

The polyamide-rubber blended composition of the present invention maycontain carbon black, white filler, plasticizer and processing aid(s)for the purpose of providing further improved strength andprocessability. If desired, the composition may also contain variousadditives such as stabilizers and color pigments which are commonly usedwith resins and rubbers.

Examples of the polyepoxy compound as component (c) of the compositionof the present invention include diglycidyl or polyglycidyl ether ofbisphenol A, bisphenol F, resorcinol novolak type phenol-formaldehyde orcyclohexanedimethanol, diglycidyl or polyglycidyl ethers of aliphaticpolyhydric alcohol such as ethylene glycol, propylene glycol, neopentylglycol, 1,6-hexanediol, glycerol, trimethylolpropane, diglycerol,polyglycerol or sorbital, or modified compounds thereof such asdibromoneopentyl glycol diglycidyl ether; diglycidyl or polyglycidylethers of cyclic compounds such as vinylcyclohexenedioxide; diglycidylor polyglycidyl esters such as diglycidyl phthalate; oligomers havingepoxy groups at their side chains such as polyvinyl glycidyl etheroligomers, polyallyl glycidyl ether oligomers, or polyglycidylmethacrylate oligomers; tri(2,3-epoxypropyl)phosphate; triglycidylisocyanurate; diglycidyl melamine; and polyglycidyl derivatives. Thesepolyepoxy compounds may be used alone or in combination thereof. Ofthese, diepoxy compounds of the bisphenol A type; diepoxy compounds suchas ethylene glycol diglycidyl ether, propylene glycol diglycidyl etherand phthalic acid diglycidyl ester; trifunctional and higher-degreefunctional polyepoxy compounds such as triglycidyl isocyanurate,glycerol polyglycidyl ether and sorbitol polyglycidyl ether arepreferably used. These polyepoxy compounds must be added in an amount ofat least 0.1 parts by weight, preferably not less than 0.3 part byweight, in terms of the weight of the epoxy group for 100 parts byweight of the rubber composition (a). If the amount of the polyepoxycompound is less than 0.1 parts by weight in terms of the weight of theepoxy group, the resulting polyamide-rubber blended composition has muchreduced resistance to ozone and stress whitening.

The preferred polyepoxy compound is such that the cross-linking of thecarboxyl nitrile rubber and hydrin rubber is completed by kneading forabout 5-30 minutes in the presence of said polyepoxy compound. If therate of cross-linking of these rubbers is very fast, the rubbers arecross-linked before they are thoroughly dispersed in the polyamideresin, and the homogeniety of the resulting blend composition issignificantly impaired. If the rate of cross-linking is too slow, therubbers are deteriorated.

Components (a), (b) and (c) are blended in any of the devices thatpermit controlled heating at temperatures higher than the melting pointof the polyamide resin (b), such as Banbury mixer, pressure kneader,Brabender mixer, kneader extruder and heat transfer rolls. After heatingthese devices to a temperature higher than the melting point of thepolyamide resin, this resin, as well as the carboxyl nitrile rubber,hydrin rubber, polyepoxy compound and any suitable additives are chargedinto the vessel and kneaded until the rubbers are thoroughlycross-linked to provide a homogeneous blended composition.

In a preferred embodiment, the carboxyl nitrile rubber and hydrin rubberare kneaded in a common rubber mixer such as a Banbury mixer, openrolls, pressure kneader or Brabender mixer, and thereafter, thepolyamide resin is blended into the mixture under heating in thepresence of the cross-linking agent. This method is effective forproviding a blended composition having further improved resistance toozone and stress whitening. mixing the polyepoxy compound with therubbers before they are blended with the polyamide resin is notpreferred because this causes a decrease in the resistance of the finalcomposition to stress whitening and ozone. For example, the polyamideresin is preferably mixed with a premixture of the carboxyl nitrilerubber and hydrin rubber under heating for a period of 5-10 minutes, andthereafter, the polyepoxy compound is added to the mixed blend, and thefinal mixture is kneaded under heating.

Typical working examples of the present invention as well as ComparativeExamples are shown below.

EXAMPLES 1 TO 20 AND COMPARATIVE EXAMPLES 1-16

In Examples 1 to 20, the carboxyl nitrile rubbers, hydrin rubbers, andnickel diethyl dithiocarbamate (a stabilizer) listed in Tables 1 to 4were charged into a Brabender mixer in the proportions indicated. Eachformulation was mixed for 5 minutes at a rotor speed of 60 rpm while thetemperature in the chamber was held at 60° C.

The resulting rubber compositions and the polyamide resins identified inTables 1 to 4 were weighed in the proportions listed in the tables, andcharged into a Brabender mixer and mixed at a rotor speed of 80 rpmwhile the temperature in the chamber was held at 190° C. After 10-minutemixing, a polyepoxy compound (a cross-linking agent) was added,whereupon the mixing torque increased to a maximum value and thereafterdecreased. The mixing was continued until the torque almost reached asteady value. In Examples 1 to 20, the rubber compositions and thepolyamide resins were mixed for 15 minutes after the addition of thepolyepoxy compound.

In Comparative Examples 1 to 16, the nitrile rubbers and/or hydrinrubbers and stabilizers shown in Tables 1 to 4 were mixed for 5 minutesin the proportions also shown in Tables 1 to 4. The so prepared rubbercompositions where then mixed for 10 minutes under heating with thepolyamide resin shown in the Tables. After adding one or more ofm-phenylene bis-maleimide, dibenzothiazyl disulfide and Epikote 828 as across-linking agent or accelerator, the mixing was continued for anadditional 15 minutes. No cross-linking agent was used in ComparativeExample 13, wherein the polyamide resin and the rubber compositioncharged into the mixer were simply kneaded for minutes. The sample ofComparative Example 15 was made of the polyamide resin alone.

The physical properties (tensile strength and elongation at break) ofthe samples prepared in the Examples and Comparative Examples, as wellas their resistance to ozone and stress whitening, are shown in Tables 1to 4.

The sample of Comparative Example 1 shown in Table 1 was a blendedcomposition of nylon and common carboxyl-free nitrile rubber. Cracksdeveloped in the surface of this sample when it was subjected to 20hours of cyclic application of 0-30% elongation. This shows that thesample will perform very poorly upon exposure to ozone under hostileconditions.

The sample of Comparative Example 2 was a ternary blended composition ofcommon carboxyl-free nitrile rubber, hydrin rubber and the polyamideresin. The sample of Comparative Example 3 was a blend of the hydrinrubber and the polyamide resin. The sample of comparative Example 4 wasa ternary blend of a carboxyl-containing nitrile rubber, hydrin rubberand the polyamide resin. These three samples had a slightly improvedozone resistance as compared with the sample of Comparative Example 1,but the improvement was not as great as desired. Furthermore, the sampleof Comparative Example 3 was very low in the resistance to stresswhitening.

The samples of Comparative Examples 5 to 10 and Examples 1 to 5 wereblended compositions using the carboxy nitrile rubber, hydrin rubber andthe polyepoxy compound (as cross-linking agent for the polyamide resin).When the proportion of the hydrin rubber was 70 to 30 vol% of the totalvolume of the rubber composition as in Examples 1 to 5, the ozoneresistance was far better than that obtained in Comparative Examples 1to 4. The samples of Examples 1 to 5 also had high resistance to stresswhitening. However, no improvement in ozone resistance was obtained whenthe proportion of the hydrin rubber was more than 70 vol% or less than30 vol% of the total volume of the rubber composition (ComparativeExamples 5 to 10).

Table 2 shows the effects of the carboxyl content of the nitrile rubber(Comparative Examples 11 and 12, and Examples 6 and 3), as well as theeffects of the amount of polyepoxy compound as the cross-linking agent(Comparative Examples 13 and 14, and Examples 7 to 9 and 3) on theresistance to ozone and stress whitening of the final polyamide-rubberblend composition. When the content of the carboxyl group in the nitrilerubber was less than 0.7 wt% as in Comparative Examples 11 and 12, nogreat improvement in the ozone resistance was achieved. Furthermore, inComparative Example 11, the polyamide resin was cross-linked by thepolyepoxy compound and the resulting blend was so poorly thermoplasticthat its shaping was practically impossible. The samples of Examples 6and 3 containing more than 0.7 wt% of the carboxyl group in the nitrilerubber exhibited an appreciable improvement in the resistance to ozoneand stress whitening. In Comparative Examples 13 and 14, the polyepoxycompound was added in an amount of less than 0.1 parts by weight, interms of the weight of the epoxy group, per 100 parts by weight of thecombination of the carboxyl nitrile rubber and hydrin rubber. Theresistance to ozone and stress whitening of the two comparative sampleswas very low. On the other hand, Examples 7 to 9 and 3 using more than0.1 parts by weight of the polyepoxy compound in terms of the weight ofthe epoxy group provided blended compositions having improved resistanceto zone and stress whitening.

Table 3 shows the effect of the volume proportion of the rubbercomposition with respect to the final polyamide-rubber blendedcomposition. When the proportion of the rubber composition was less than20 vol% of the blend, a high 50% tensile stress occurred and noimprovement in the flexibility of the polyamide resin was attained. Ifthe proportion of the rubber composition was more than 70 vol% of theblend (as in Comparative Example 16), the thermoplasticity of the blendwas so low as to make its shaping impossible.

Table 4 shows the results of samples according to the present inventionusing glycidyl terephthalate or triglycidyl isocyanurate instead ofEpikote 828 as the cross-linking agent; epichlorohydrin-allyl glycidylether copolymer or epichlorohydrin-ethylene oxide copolymer instead ofepichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer as thehydrin rubber; and nylon 11 instead of nylon 12 as the polyamide resin.All of the modified samples exhibited high resistance to ozone andstress whitening.

The polyamide-rubber blended composition of the present inventionprovides a product having high flexibility and strength, as well as thesignificant resistance to ozone, stress whitening, thermal aging andgasoline. Therefore, the composition of the present invention will findextensive use in resin and rubber products in automotive enginecompartments and other products that are subjected to great strain dueto vibration and which are used at elevated temperatures under exposureto gasoline or gasoline vapor.

    TABLE 1      Com- Com- Com- Com- Com- Com- Com-      Com- Com- Com- parative     parative parative partative parative parative parative      parative     parative parative Example Example Example Example Example Example     Example Example Example Example Example Example Example Example Example     1 2 3 4 5 6 7 1 2 3 4 5 8 9 10       Composition (parts by weight)                Nylon 12*.sup.1 40 40 40     40 40 40 40 40 40 40 40 40 40 40 40 Nitrile rubber No. 1*.sup.2 60 30 --     -- -- -- -- -- -- -- -- -- -- -- -- Nitrile rubber No. 4*.sup.3 -- -- --     30 60 50 45 40 35 30 25 20 15 10 Hydrin rubber No. 1*.sup.4 -- 40 80 40     -- 13 20 27 33 40 47 53 60 67 80 Epikote 828*.sup.5 -- -- -- -- 1.5 1.5     1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Nickel diethyldithiocarbamate 1 1 1     1 1 1 1 1 1 1 1 1 1 1 1 m-Phenylenebismaleimide 2 2 2 2 -- -- -- -- --     -- -- -- -- -- -- Dibenzothiazyl disulfide 1 1 1 1 -- -- -- -- -- -- --     -- -- -- -- Stearic acid 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5     0.5 0.5 0.5 Content of carboxyl group 0 0 -- 0 2.62 2.62 2.62 2.62 2.62     2.62 2.62 2.62 2.62 2.62 -- in nitrile rubber (wt %) Epoxy group content     0 0 0 0 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57 0.57 (parts by     wt.) Polymer composition (vol %)*.sup.6 Overall rubber volume ratio 60     60 60 60 60 60 60 60 60 60 60 60 60 60 60 Nitrile rubber volume ratio     100 50 0 50 100 83 75 67 58 50 42 33 25 17 0 Hydrin rubber volume ratio     0 50 100 50 0 17 25 33 42 50 58 67 75 83 100 Initial physical properties*     .sup.7 Tensile strength (kg/cm.sup.2) 262 235 121 245 Shaping 248 250     270 230 204 175 144 120 115 Shaping Elongation at break (%) 280 280 200     310 impossible 340 350 350 320 310 260 210 190 180 impossible Ozone     resistance*.sup.8 Cracking time (hrs) 20 189 106 136  96 116 320 500 500     212 50 48 Resistance to stress whitening*.sup.9 Percent elongation for     Not Not 60 Not  Not Not Not Not Not Not 80 30 30 whitening whitened     whitened  whitened  whitened whitened whitened whitened whitened     whitened Degree of whitening   B         A B B     Notes to Table 1:     *.sup.1 Polylauryllactam; "L1940" of Daicel Chemical Industries, Ltd.     *.sup.2 Acrylonitrilebutadiene copolymer rubber; experimental product,     bound acrylonitrile = 40 wt %, Mooney viscosity, ML.sub.1 + 4 (100.degree      C.) = 52     *.sup.3 Carboxylcontaining acrylonitrilebutadiene copolymer rubber;     experimental product, bound acrylonitrile = 40 wt %, carboxyl group     content = 2.62 wt % (in monomeric methacrylic acid), Mooney viscosity,     ML.sub.1 + 4 (100° C.) = 46     *.sup.4 Epichlorohydrinethylene oxideallyl glycidyl ether copolymer     rubber; Zecron 3100 of The Japanese Geon Co., Ltd.     *.sup.5 Polyepoxy compound of bisphenol A type; product of YukaShell Co.,     Ltd.     *.sup.6 Overall rubber volume ratio = (V.sub.N + V.sub.E)/(V.sub.N +     V.sub.E + V.sub.A) × 100; Nitrile rubber volume ratio = V.sub.N     /(V.sub.N + V.sub.E) × 100; Hydrin rubber volume ratio = V.sub.E     /(V.sub.N + V.sub.E) × 100;     wherein V.sub.N, V.sub.E and V.sub.A represent the volumes of nitrile     rubber, hydrin rubber and polyamide resin, respectively, ia a unit blend     composition.     *.sup.7 at 20 ± 3° C. and a drawing speed of 50 mm/min     *.sup.8 The sample deteriorated at an ozone concentration of 50 ± 5     pphm, elongation of 0-30%, cyclic strain of 60 rpm and temperature of 40     ± 2° C. The time when cracking was found to occur by observatio     at magnification 10 was designated cracking time.     *.sup.9 The sample was drawn at a speed of 50 mm/min (20 ± 3°     C.), and percent elongation at which the sample turned white was     designated percent elongation for whitening. The rating indices for     whitening were as follows:     A -- The sample whitened only slightly and most of it was transparent.     B -- The sample whitened extensively and turned opaque.

Method of Forming Test Piece Sheets And Conditions of Their Annealing

A sample material sandwiched between aluminum foils was placed in a mold(210° C.); after preheating for 2 minutes, the material was pressedunder a oil press (ca. 100 kg/cm²) for 10 minutes; the resulting sheet 1mm thick was removed from the mold, quenched with water and stripped ofthe aluminum foils. The sheet without aluminum foils was then annealedin vacuum at 150° C. for 1 hour.

                                      TABLE 2                                     __________________________________________________________________________                     Com-  Com-           Com- Com-                                                parative                                                                            parative       parative                                                                           parative                                            Example                                                                             Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                              11    12   6    3    13   14   7    8    9                   __________________________________________________________________________    Composition (parts by weight)                                                 Nylon 12*.sup.1  40    40   40   40   40   40   40   40   40                  Nitrile rubber No. 1*.sup.2                                                                    30    --   --   --   --   --   --   --   --                  Nitrile rubber No. 2*.sup.3'                                                                   --    30   --   --   --   --   --   --   --                  Nitrile rubber No. 3*.sup.4'                                                                   --    --   30   --   --   --   --   --   --                  Nitrile rubber No. 4*.sup.3                                                                    --    --   --   30   30   30   30   30   30                  Hydrin rubber No. 1*.sup.4                                                                     40    40   40   40   40   40   40   40   40                  Epikote 828*.sup.5                                                                             1.5   1.5  1.5  1.5       0.25 0.5  1    2.0                 Nickel diethyldithiocarbamate                                                                  1     1    1    1    1    1    1    1    1                   Stearic acid     0.5   0.5  0.5  0.5  0.5  0.5  0.5  0.5  0.5                 Content of carboxyl group                                                                      0     0.63 1.83 2.62 2.62 2.62 2.62 2.62 2.62                in nitrile rubber (wt %)                                                      Epoxy group content (parts by wt.)                                                             0.57  0.57 0.57 0.57 0    0.09 0.19 0.38 0.76                Polymer composition (vol %)*.sup.6                                            Overall rubber volume ratio                                                                    60    60   60   60   60   60   60   60   60                  Nitrile rubber volume ratio                                                                    50    50   50   50   50   50   50   50   50                  Hydrin rubber volume ratio                                                                     50    50   50   50   50   50   50   50   50                  Initial physical properties*.sup.7                                            Tensile strength (kg/cm.sup.2)                                                                 --    121  160  204  118  132  142  165  216                 Elongation at break (%)                                                                        --    190  260  310  240  260  270  300  290                 Ozon resistance*.sup.8                                                                         Shaping                                                      Cracking time (hrs)                                                                            impossible                                                                          42   320  ≧500                                                                        22   120  286  ≧500                                                                        ≧500         Resistance to stress whitening*.sup.9                                         Percent elongation for                                                                         --    30   80   Not  50   100  Not  Not  Not                 whitening (%)                    whitened       whitened                                                                           whitened                                                                           whitened            Degree of whitening                                                                            --    B    A         B    A                                  __________________________________________________________________________     Notes to Table 2:                                                              *.sup.1 to *.sup.9 See the notes to Table 1.                                 *.sup.3' Carboxyl-containing acrylonitrilebutadiene copolymer rubber:         experimental product, bound acrylonitrile = 40 wt %, content of carboxyl      group = 0.63 wt % (in monomeric methacrylate acid), Mooney viscosity,         ML.sub.1 + 4 (100° C.) = 48                                            *.sup.4' Carboxyl-containing acrylonitrilebutadiene copolymer rubber:         experimental product, bound acrylonitrile = 40 wt %, content of carboxyl      group = 1.83 wt % (in monomeric methacrylate acid), Mooney viscosity,         ML.sub.1 + 4 (100° C.) = 50                                       

                                      TABLE 3                                     __________________________________________________________________________                    Compara-                            Compara-                                  tive                                tive                                      Example                                                                             Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                   15    10   11   12   13   3    14   16                        __________________________________________________________________________    Composition (parts by weight)                                                 Nylon 12*.sup.1 100   80   70   60   50   40   30   20                        Nitrile rubber No. 4*.sup.3                                                                   --    10   15   20   25   30   35   40                        Hydrin rubber No. 1*.sup.4                                                                    --    13   20   27   33   40   47   53                        Epikote 828*.sup.5                                                                            --    0.5  0.75 1    1.25 1.5  1.75 2                         Nickel diethyldithiocarbamate                                                                 --    0.33 0.5  0.67 0.83 1    1.17 1.33                      Stearic acid    --    0.5  0.5  0.5  0.5  0.5  0.5  0.5                       Content of carboxyl group                                                                     --    2.62 2.62 2.62 2.62 2.62 2.62 2.62                      in nitrile rubber (wt %)                                                      Epoxy group content                                                                           --    0.57 0.57 0.57 0.57 0.57 0.57 0.57                      (parts by wt.)                                                                Polymer composition (vol %)*.sup.6                                            Overall rubber volume ratio                                                                    0    20   30   40   50   60   70   80                        Nitrile rubber volume ratio                                                                   50    50   50   50   50   50   50   50                        Hydrin rubber volume ratio                                                                    50    50   50   50   50   50   50   50                        Initial physical properties*.sup.7                                            50% tensile stress (kg/cm.sup.2)                                                              321   246  221  154  106  79   62   Shape                     Tensile strength (kg/cm.sup.2)                                                                --    --   322  264  226  204  142  impossible                Elongation at break (%)                                                                       --    --   290  290  290  310  260                            Ozone resistance*.sup.8                                                       Cracking time (hrs)                                                                           ≧500                                                                         ≧500                                                                        ≧500                                                                        ≧500                                                                        ≧500                                                                        ≧500                                                                        ≧500                    Resistance to stress whitening*.sup.9                                         Percent elongation for                                                                        Not   Not  Not  Not  Not  Not  Not                            whitening (%)   whitened                                                                            whitened                                                                           whitened                                                                           whitened                                                                           whitened                                                                           whitened                                                                           whitened                       Degree of whitening                                                           __________________________________________________________________________     (Notes)                                                                       *.sup.1, *.sup.3 to *.sup.9 See the corresponding notes to Table 1.      

                                      TABLE 4                                     __________________________________________________________________________                      Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                         3    15   16   17   18   19   20                            __________________________________________________________________________    Composition (parts by weight)                                                 Nylon 12*.sup.1   40   40   40   40   40   --   40                            Nylon 11*.sup.2   --   --   --   --   --   40   --                            Nitrile rubber No. 4*.sup.3                                                                     30   30   30   30   30   30   --                            Nitrile rubber No. 5*.sup.3'                                                                    --   --   --   --   --   --   30                            Hydrin rubber No. 1*.sup.4                                                                      40   40   40   --   --   --   40                            Hydrin rubber No. 2*.sup.4'                                                                     --   --   --   40   40   --   --                            Hydrin rubber No. 3*.sup.4"                                                                     --   --   --   --   --   40   --                            Epikote 828*.sup.5                                                                              1.5  --   --   1.5  1.5  1.5  1.5                           Terephthalic acid diglycidyl ester                                                              --   1    --   --   --   --   --                            Triglycidyl diisocyanurate                                                                      --   --   0.5  --   --   --   --                            Nickel diethyldithiocarbamage                                                                   1    1    1    1    1    1    1                             Stearic acid      0.5  0.5  0.5  0.5  0.5  0.5  0.5                           Content of carboxyl group                                                                       2.62 2.62 2.62 2.62 2.62 2.62 3.1                           in nitrile rubber (wt %)                                                      Epoxy group content (parts by wt.)                                                              0.57 0.43 0.41 0.57 0.57 0.57 0.57                          Polymer composition (vol %)*.sup.6                                            Overall rubber volume ratio                                                                     60   60   60   60   60   60   60                            Nitrile rubber volume ratio                                                                     50   50   50   50   49   50   50                            Hydrin rubber volume ratio                                                                      50   50   50   50   51   50   50                            Initial physical properties*.sup.7                                            Tensile strength (kg/cm.sup.2)                                                                  204  198  215  205  175  226  206                           Elongation at break (%)                                                                         310  300  290  320  270  310  290                           Ozone resistance*.sup.8                                                       Cracking time (hrs)                                                                             ≧500                                                                        ≧500                                                                        ≧500                                                                        ≧500                                                                        ≧500                                                                        ≧500                                                                        ≧500                   Resistance to stress whitening*.sup.9                                         Percent elongation for whitening (%)                                                            Not  Not  Not  Not  Not  Not  Not                           Degree of whitening                                                                             whitened                                                                           whitened                                                                           whitened                                                                           whitened                                                                           whitened                                                                           whitened                                                                           whitened                      __________________________________________________________________________     Notes to Table 4:                                                             *.sup.1, *.sup.3, *.sup.4, *.sup.5 to *.sup.9 See the corresponding notes     to Table 1.                                                                   *.sup.2 Condensation polymer of 11amino-undecanoic acid: "BESNO-TL" of        Lilsan Co., Ltd.                                                              *.sup.3' Carboxyl-containing acrylonitrilebutadiene copolymer rubber:         "Nipol 1072" of The Japanese Geon Co., Ltd., bound acrylonitrile = 27 wt      %, carboxyl group content = 3.1 wt %, Mooney viscosity, ML.sub.1 + 4          (100° C.) = 48                                                         *.sup.4' Epichlorohydrin-allyl glycidyl ether copolymer rubber: "Zecron       1100" of The Japanese Geon Co., Ltd.                                          *.sup.4" Epichlorohydrin-ethylene oxide copolymer rubber: "Herchlor C" of     Hercules Incorporated                                                    

What is claimed is:
 1. An polyamide-rubber blended composition havingimproved resistance to ozone, stress whitening and gasoline prepared bymixing together with heating the following components:(a) from 70 to 20volume percent of a rubber composition consisting of:(i) 30 to 70 volumepercent of an acrylonitrile-butadiene copolymer rubber containing atleast 0.7 weight percent of a carboxyl group in the polymer, and (ii) 70to 30 volume percent of an epichlorohydrin rubber; (b) 30 to 80 volumepercent of a polyamide resin; and (c) at least 0.1 parts by weight of apolyepoxy compound in terms of the weight of the epoxy group per 100parts by weight of the rubber composition of component (a).
 2. Thepolyamide-rubber blended composition of claim 1 in which component (i)is a carboxyl-containing acrylontrile-butadiene copolymer rubber havinga bound acrylonitrile content of 10 to 55 weight percent and a glasstransition point of not more than 10° C.
 3. The polyamide-rubber blendedcomposition of claim 1 in which the epichlorohydrin rubber of component(a) is a homopolymer of epichlorohydrin, a copolymer of epichlorohydrinand ethylene oxide, a copolymer of epichlorohydrin and propylene oxideor a terpolymer of epichlorohydrin, ethylene or propylene oxide andallylglycidyl ether.
 4. The polyamide-rubber blended composition ofclaim 1 in which the polyamide resin is a crystalline thermoplasticresin having an amido bond in the polymer.
 5. The polyamide-rubberblended composition of claim 1 in which the polyamide resin ispolycaprolactam (nylon 6), polylauryllactam (nylon 12), the condensationpolymer of 11-amino undecanoic acid (nylon 12), polyhexamethyleneazelamide (nylon 6,9) or polyhexamethylene sebacamide (nylon 6,10). 6.The polyamide-rubber blended composition of claim 1 further including atleast one of carbon black, filler, plasticizer, processing aid,stabilizer or pigment.
 7. The polyamide-rubber blended composition ofclaim 1 in which component (c) is a polyepoxy compound capable ofcross-linking components (i) and (ii) by kneading within about 5 to 30minutes.
 8. The polyamide-rubber blended composition of claim 1 in whichcomponent (c) is a bisphenol A-type diepoxy, ethylene glycol diglycidylether, propylene glycol diglycidyl ether, phthalic acid diglycidylester, triglycidyl isocyanurate, glycerol polyglycidyl ether andsorbitor polyglycidyl ether.
 9. The polyamide-rubber blended compositionof claim 1 in which components (a) is mixed with component (b) and thencomponent (c) is mixed with the resulting mixture of components (a) and(b).
 10. An ozone-, stress whitening- and gasoline-resistant hosefabricated from the polyamide-rubber blended composition of claim 1.